Publications

Background Vivax malaria is the predominant form of malaria outside Africa, affecting about 14 million people worldwide, with about 2.5 billion people exposed. Development of a Plasmodium vivax vaccine is a priority, and merozoite surface protein 7 (MSP-7) has been proposed as a plausible candidate. The P. vivax genome contains 12 MSP-7 genes, which contribute to erythrocyte invasion during blood-stage infection. Previous analysis of MSP-7 sequence diversity suggested that not all paralogs are functionally equivalent. To explore MSP-7 functional diversity, and to identify the best vaccine candidate within the family, MSP-7 expression and antigenicity during bloodstream infections were examined directly from clinical isolates. Methods Merozoite surface protein 7 gene expression was profiled using RNA-seq data from blood samples isolated from ten human patients with vivax malaria. Differential expression analysis and co-expression cluster analysis were used to relate PvMSP-7 expression to genetic markers of life cycle stage. Plasma from vivax malaria patients was also assayed using a custom peptide microarray to measure antibody responses against the coding regions of 12 MSP-7 paralogs. Results Ten patients presented diverse transcriptional profiles that comprised four patient groups. Two MSP-7 paralogs, 7A and 7F, were expressed abundantly in all patients, while other MSP-7 genes were uniformly rare (e.g. 7J). MSP-7H and 7I were significantly more abundant in patient group 4 only, (two patients having experienced longer patency), and were co-expressed with a schizont-stage marker, while negatively associated with liver-stage and gametocyte-stage markers. Screening infections with a PvMSP-7 peptide array identified 13 linear B-cell epitopes in five MSP-7 paralogs that were recognized by plasma from all patients. Conclusions These results show that MSP-7 family members vary in expression profile during blood infections; MSP-7A and 7F are expressed throughout the intraerythrocytic development cycle, while expression of other paralogs is focused on the schizont. This may reflect developmental regulation, and potentially functional differentiation, within the gene family. The frequency of B-cell epitopes among paralogs also varies, with MSP-7A and 7L consistently the most immunogenic. Thus, MSP-7 paralogs cannot be assumed to have equal potential as vaccines. This analysis of clinical infections indicates that the most abundant and immunogenic paralog is MSP-7A.

Matrix (M) protein of Newcastle disease virus (NDV) is an abundant protein that can induce a robust humoral immune response. However, its antigenic epitopes remain unknown. In this study, we used a pepscan approach to map linear B cell immunodominant epitopes (IDEs) of M protein with NDV-specific chicken antisera. The six epitopes with the highest reactivity by peptide scanning were obtained as IDE candidates. Among them, aa71–85 and aa349–363 were identified by immunological assays with NDV-specific or IDE-specific antisera. The minimal antigenic epitopes of the two IDEs were further characterized as 77MIDDKP82 and 354HTLAKYNPFK363. Moreover, an amino acid sequence alignment and immunoblot analysis revealed the conservation of the two IDEs in the M protein of strains of different genotypes. These two IDEs of M protein could be genetically eliminated as negative markers in recombinant NDV for serologically differential diagnosis in the development of marker vaccines.

The use of antibody-based therapy to treat a variety of diseases and conditions is well documented. The use of antibodies as an antidote to treat tetanus infections was one of the first examples of immunotherapy and remains the standard of care for cases involving potential infections. Plasma-derived immunoglobulins obtained from human or horse pose risks of infection from undetectable emergent viruses or may cause anaphylaxis. Further, there is a lack of consistency between lots. In the search for new formulations, we obtained a series of clonally related human monoclonal antibodies (mAbs) derived from B cells sorted from donors that presented anti-tetanus neutralizing titers. Donors were revaccinated prior to blood collection. Different strategies were used for single-cell sorting, since it was challenging to identify cells at a very low frequency: memory B cell sorting using fluorescent-labeled tetanus toxoid and toxin as baits, and plasmablast sorting done shortly after revaccination. Screening of the recombinant mAbs with the whole tetanus toxin allowed us to select candidates with therapeutic potential, since mAbs to different domains can contribute additively to the neutralizing effect. Because of selective binding to different domains, we tested mAbs individually, or in mixtures of two or three, in the neutralizing in vivo assay specified by Pharmacopeia for the determination of polyclonal hyperimmune sera potency. An oligoclonal mixture of three human mAbs completely neutralized the toxin injected in the animals, signaling an important step for clinical mAb development.